The invention relates generally to a roll-bar, or rollover protection for use in passenger vehicles having a simplified construction consisting of a profile bar unit and a guide unit each defined as a structurally reinforced box profile.
To protect the occupants of passenger vehicles as well as tractors, it is known to provide vehicles with a rollover protection apparatus. In practice, two systems have become established.
The one system provides for a fixed rollover bar, sometimes referred to as "handle," spanning the entire vehicle width.
In the second system, addressed by the invention as well, each vehicle seat has an associated rollover bar, which in its rest position is hidden inside a cassette fixed to the vehicle and at the start of a rollover motion rapidly extends into a self-locking support position.
These extendable rollover bars are typically U-shaped with tubular legs that are vertically guided in standpipes of the cassettes. Inside each leg, a spiral spring is disposed, which is kept under initial tension by a holding mechanism that can be released by a rollover sensor. This causes the rollover bar to be pushed out of the cassette within a few tenths of a second by the action of the spring and to be locked in its support position. To create the U-shape nature of the bar, the two tubular legs are interconnected by a transversely extending segment, over which a padded cover is placed.
It is known from prior art (WO 95/03952) to fabricate the tubular elements of the rollover bar from high-strength steel, partly using steel tubes, partly sheet metal half shells. This construction is complex and thus costly. Furthermore, the employed structural elements are very heavy, which is not only undesirable in principle, but also requires particularly powerful driving springs for the rapid extension of the rollover bar to permit the relatively heavy bar to be brought into its support position in the shortest possible time.
A rollover bar has therefore been disclosed (DE 43 14 538 A 1) in which particularly the legs of the rollover bar and the guiding standpipes are made of extruded profiles. Since extruded profiles have the advantage of reduced weight compared to steel tubes and are cheaper to produce, this prior art rollover bar is not only comparatively light, but can also be produced at low cost.
But for rollover bars it is particularly important that the material be very rigid so as to prevent head injuries of the vehicle occupants due to buckling of the rollover bar as the vehicle turns over. Extruded profiles, however, due to the relatively soft aluminum or aluminum alloys used, are by nature easily deformable.
To increase the rigidity of the bar unit, DE 195 23 790.0 A 1 discloses the use of an extruded profile with tubular legs that are interconnected by a joining plate to form a single part. The extrusion preferably forms a spectacle-shaped profile. This profile bar unit is enclosed over part of its length by a one-piece guide block, preferably also made from a profile section. This guide block is mounted in and enclosed by a sheet metal cassette, which forms the outer housing of the rollover bar and which in turn is directly fixed to the vehicle, e.g., to the rear wall of the passenger space of a convertible.
In the aforementioned prior art, the extrusion defining the bar spans the entire width of the bar with its profile. Nevertheless, this prior art profile corresponds to the typical basic structure of a rollover bar with two tubular leg parts, in each of which a spring mechanism is disposed and approximately 3/4 of the circumference of each encloses a standpipe, which is attached to the floor of the cassette.
In addition to the guidance of the profile bar unit by means of its bar legs in the standpipes, the guide block is provided with four plastic sliding elements disposed in recesses, which are in sliding contact with the profile bar unit to guide it.
In the clearance between the bar legs, a toothed rack is centrally mounted on the profile bar unit. This rack interacts with a locking pawl pivotably mounted on the guide block in the locking mechanism housing vertically to the width of the bar unit and actively engageable with the teeth of the rack by means of two catch springs such that the profile bar unit can at any time be extended upwardly into its support position in that the locking pawl moves across the teeth of the rack, whereas any downward motion in the direction of the basic position is prevented due to the active engagement of the pawl with the respective tooth of the rack. The rack in combination with the locking pawl thus serves to automatically lock the rollover unit into its support position when a force is applied to the profile bar unit as a result of an overturn.
On the locking mechanism housing of the guide block, an unlocking pawl is furthermore pivotably mounted in the same plane as the locking pawl, which with a hook-shaped nose actively engages with a pin on the profile bar unit and thus holds the latter in the locked basic position against the force of the pretensioned drive spring. This unlocking pawl is associated with a power element, for example, a pin-expelling pyrotechnically actuated cartridge or a crash magnet, which, activated by a rollover sensor, mechanically brings the unlocking pawl out of its engagement with the pin on the profile bar unit and thus triggers the extension motion of the profile bar unit in the event of a crash.
On the upper end face of the profile bar unit, a cross strut is mounted, which is covered by an unpadded plastic cap.
Since in the prior art profile bar, the wall thickness of the joining plate between the two tubular bar leg profile components is relatively thin, the rigidity against buckling must be entirely provided by the tubular bar leg profile components, which requires a relatively large diameter and wall thickness. Thus, the depth of the profile and consequently that of the exterior guide mechanism or cassette receiving it is relatively large.
Due to the profile shape of the prior art bar unit, the bar leg profile components enclose the standpipe only partly at a tight distance so that guidance by the standpipes is insufficient and additional means for guidance must be provided.
Furthermore, due to the profile shape, each leg must be provided with its own drive in conventional manner. As a result, drive complexity is exactly comparable to that of a rollover protection system with U-shaped rollover bar.
In the prior art case, the guide block is made relatively short in axial direction. As a result, an additional component, the cassette, is required to receive the guide block and the profile bar unit.
The plastic cover, since it is unpadded, cannot dampen the impact of the head of a vehicle occupant.